Lubricating oil flow control for a rotary compressor

ABSTRACT

A rotary compressor adapted especially for pumping fluids in a closed circuit of an air conditioning system comprising a pair of meshing helical rotors adapted for rotation about parallel axes and a lubrication oil flow path including registering oil ports in one of said rotors and in an adjacent housing wall whereby fluid is admitted to the lubrication oil circuit intermittently at a rate that is dependent upon the speed of the rotors thereby providing a desired higher lubricating oil flow at high compressor speeds and a reduced flow at lower compressor speeds to establish lubrication, sealing and cooling of the relatively movable parts of the compressor.

United States Patent [191 Kantz [451 May 29, 1973 [75] Inventor: Don B. Kantz, Ferndale, Mich.

[73] Assignee: Ford Motor Company, Dearborn,

Mich.

221 Filed: Mar. 29, 1972 21 Appl. No.: 239,064

[52] US. Cl. ..418/77, 184/616, 418/99 [51] Int. Cl. ..F04c 17/00 [58] Field of Search ..62 /469; 184/616;

[56] References Cited UNITED STATES PATENTS 3,518,975 7/1970 Schmidt ..418/97 X 3,649,140 1,706,829

Schibbye ..41 8/99 X Bitzer ..41 8/88 X Primary Examiner-Manuel A. Antonakas Attorney-Keith L. Zerschling and Donald J.

H arrington [57] ABSTRACT A rotary compressor adapted especially for pumping fluids in a closed circuit of an air conditioning system comprising a pair of meshing helical rotors adapted for rotation about parallel axes and a lubrication oil flow path including registering oil ports in one of said rotors and in an adjacent housing wall whereby fluid is admitted to the lubrication oil circuit intermittently at a rate that is dependent upon the speed of the rotors thereby providing a desired higher lubricating oil flow at high compressor speeds and a reduced flow at lower compressor speeds to establish lubrication, sealing and cooling of the relatively movable parts of the compressor.

4 Claims, 10 Drawing Figures PATENTEDMAYZQ I973 3. 736. 079

SHEET 1 OF 3 PATENTEDHAYZQ ms 3. 736, 079

SHEET 2 {1F 3 PATENTEUMAY 2 9 1975 SHEET 3 OF 3 LUBRICATING OIL FLOW CONTROL FOR A ROTARY COMPRESSOR GENERAL DESCRIPTION OF THE INVENTION The improvements of my invention relate generally to rotary compressors of the Lysholm type. Reference may be made, for example, to US. Pat. No. 2,174,522 for an illustration of a Lysholm type rotor for compressing compressible fluids. Such compressors require the presence of lubricating oil to establish sealing between the rotor members and the surrounding compressor housing and also between the meshing parts of the two rotors. The rotors comprise helical teeth, one rotor having internal helical teeth and the other having registering external helical teeth. Lubricating oil is necessary also to reduce friction and to provide the necessary cooling. The oil is capable of carrying away heat generated due to the compression of the compressible fluid. The heat is dissipated as the oil is circulated through the lubricating oil circuit.

The oil is returned to a sump and is forced to the inlet side of the lubricating oil circuit by the discharge pressure of the compressor. The oil then is recycled.

It is the practice in some cases to provide a lubricating oil pump for supplying fluid to the inlet side of the lubricating oil circuit and to drive the lubricating oil pump, which may be a positive displacement pump, by connecting it mechanically through'a drive system to one of the rotor members.

A flow restricting control orifice is provided on the inlet side of the lubricating oil circuit in prior art arrangements. Because the pressure drop across the oriflce is substantially uniform, the oil flow for lubricating, sealing and cooling the compressor is relatively constant. The oil flow requirements during high speed operation are substantially greater than the requirements for low speed operation. The lubricating system, therefore, must be calibrated to satisfy the maximum flow requirements at high speeds. This results in a generally inefficient lubricating oil system at lower speeds since excess oil is pumped.

It is an object of my invention to provide a rotary screw compressor wherein provision is made for improving the mechanical efficiency and pumping efficiency at low speeds. I accomplish this by providing multiple metering chambers at one end of one of the rotor members. The portion of the housing adjacent the end of that rotor member is provided with a lubricating oil inlet chamber which communicates with the lubricating oil inlet port, which in turn communicates with the oil sump in the air conditioner system. The metering chambers in the rotor member are charged with lubricating oil as each chamber successively registers with the lubricating oil chamber in the adjacent housing wall. Oil in the chamber then is carried to a discharge point where it is centrifuged into the compressor cavity and mixed with the compressed fluid, which in some instances is Freon gas. As the rotor speed increases, the frequency of the discharge increases. Correspondingly, a decrease in rotor speed will result in a decrease in the rate of lubricating oil supply.

This pumping action is accomplished without the addition of extraneous pumping elements and without the necessity for providing a calibrated fluid flow circuit for the lubricating oil.

The compressor efficiency is determined in part by the amount of Freon gas that becomes dissolved in the lubricating oil as the latter traverses the lubricating oil circuit. This represents a short-circuit for the compressed gas, and the presence of the short-circuit decreases the compressor efficiency since the Freon gas that is dissolved cannot be used for cooling purposes. If the rate of lubricating oil flow is decreased at lower speeds, the short-circuiting losses due to the loss of compressed Freon gas is reduced.

in conventional systems the pressure at which the lubricating oil is supplied to the system tends to increase at low speeds because of the higher back pressure that then develops in the condenser. The condenser receives, in most instances, an inadequate air supply for cooling purposes when the compressor is operated at low speed. This tends to aggravate the lubricating oil losses at low speeds since the presence of a higher oil pressure tends to cause an increased rate of flow of lubricating fluid to the compressor mechanisms when any increased flow is not required.

The improved system of my invention also overcomes mechanical and pumping horsepower losses that accompany some prior art systems that require the presence of a positive displacement lubricating oil supply pump.

GENERAL DESCRIPTION OF THE FIGURES OF THE DRAWING FIG. 1 shows a side elevation view of a compressor that is capable of using the improvements of my invention.

FIG. 2 is an end view of the compressor shown in FIG. 1.

FIG. 3 is a cross-sectional view taken along the plane of section line 3-3 of FIG. 2.

FIG. 4 is a partial side elevation view as seen from the plane of section line 44 of FIG. 2.

FIG. 5 is a cross-sectional view taken along the plane of section line 55 of FIG. 4.

FIG. 6 is a schematic representation of the ends of the rotors shown in FIG. 3 acting in their respective rotor chambers in the compressor housing.

FIG. 7 is a detailed view of an externally threaded helical rotor of the assembly of FIG. 3.

FIG. 8 is an end view of the rotor of FIG. 7.

FIG. 9 is a detail view of the other rotor shown in the assembly view of FIG. 3.

FIG. 10 is an end view of the rotor of FIG. 9.

PARTICULAR DESCRIPTION OF THE INVENTION The compressor shown in FIG. 1 is adapted to be used in an automotive vehicle air conditioning system. It includes a compressor housing 10 which is adapted to be mounted in a stationary portion of the vehicle chassis in the engine compartment of the vehicle. It includes a drive pulley 12 which can be connected to the vehicle engine crankshaft by a suitable drive belt. Numeral l4 designates the housing 4. An electromagnetic clutch structure can be applied and deactivated to establish a driving connection between pulley l2 and the drive rotor of the compressor. There are two rotors, one of which is the drive rotor 26, mounted within the housing 10. Numeral 16 designates an end plate for closing the rotor chambers within the housing 10.

An inlet port 18 for the compressor is shown in FIGS. 4 and 5. Port 18 is formed in housing 10 as part of an integral casting. It is defined in part by a fitting 20 which is connected to a Freon fluid conduit. Port 18 communicates with rotor chamber 22 in the main housing 10, as indicated in FIG. 5.

An outlet port 24 also is formed in the cover 16 as part of an integral casting. A helical rotor 26 is mounted within rotor chamber 28. Rotor 26 meshes with a second helical rotor 30 mounted for rotation about an axis parallel to the axis of rotor 26. Rotor 26 comprises external helical threads which register with internal helical threads on driven rotor 30. The periphery of the threads for rotor 26 are in close registry contact with the wall of the chamber 28 and sealed with an oil film. A corresponding sliding contact occurs between the periphery of the internal helical threads 30 and the wall of the rotor chamber 32. A suitable lubricating oil film is disposed between the relatively movable surfaces.

One axial end of the rotor 30 is provided with radially extending metering chambers 34, 36 and 38. The radially inward ends of the chamber 34, 36 and 38 register with a lubricating oil inlet collector port 40 formed in the adjacent wall of the cover 15. Port 40 communicates with oil inlet passage 42, which in turn communicates with the oil sump not shown. The radially outward end of metering chambers 34, 36 and 38 communicate with a lubricating oil discharge chamber 44 formed in the adjacent face of the cover 16 in the general region of the rotor chamber 28. The radial disposition of the chamber 44 with respect to the axis of rotation of the rotor 30 is such that a portion of the end face of the rotor 30 covers a portion of the chamber 44 where the remaining portion of the chamber 44 is exposed at all times to the chamber 28.

As the rotor 30 rotates about its axis,'the metering chambers 34, 36 and 38 selectively register with the port 40. Oil inlet pressure then is admitted to each of the chambers selectively thereby filling the chambers. Upon continued rotation of the rotor 30, each of the chambers selectively registers with the chamber 44. Oil under centrifugal pressure in the chambers 34, 36 and 38 then is centrifuged outwardly into the chamber 28. There the oil mixesv with the compressed Freon and is distributed throughout the surfaces of the rotors and the registering surfaces of the rotor chambers. This oil provides an effective rotor seal between the rotors and between the rotors and the chamber walls. It also lubricates the relatively movable surfaces and carries away heat due to the compression of the fluid and due to the mechanical friction.

Upon an increase in the speed of rotation of the rotors, the frequency of the discharges from the metering chambers increases thereby increasing the total fluid flow through the lubricating circuit. The lubricating flow requirements increase as the speed increases and the increased metering action provides the necessary volume. Conversely the flow of lubricating oil decreases at lower speeds when the lubricating oil flow requirements are reduced.

Rotor 26 acts as a driving rotor. It is connected to or formed integrally with driveshaft 46 to which is splined a clutch driveplate 48. The rotor carriesan electromagnetic winding 50 which is adapted to establish a flux field when it is energized thereby establishing a driving connection between driveplate 48 and armature 52. Driveplate 48, in turn, is connected to power input shaft 54 which in turn carries drive pulley l2. Pulley 12 is journalled by bearing 56 on a stub shaft 58 which forms a part of a clutch housing 14.

Having thus described a preferred form of my invention what I claim and desire to secure by US. Letters Patent is:

1. A rotary compressor for gaseous fluids comprising a first pump rotor with external helical teeth, a second pump'rotor with internal helical teeth, the helical teeth on said rotors registering with each other as they rotate about parallel axes, a rotor housing, a pair of rotor chambers communicating with each other formed in said housing, one chamber receiving the external tooth rotor and the second chamber receiving the internal tooth rotor, said housing including an end wall closing said rotor chambers, said wall being disposed adjacent end surfaces on said rotors, the end surface on one of said rotors having formed therein radially disposed metering chambers, a lubricating oil inlet chamber formed in said wall at a radial location where it is adapted to register with radially inward portions of said metering chamber, said lubricating oil inlet chamber being in fluid communication with a lubricating oil supply passage, a fluid discharge chamber formed in said wall at a radially outward location relative to the axis of rotation of said one rotor and arranged to register with the radially outward portions of said metering chambers as said rotors rotate, said discharge chamber being in communication with said rotor chambers whereby metered quantities of fluid are discharged therethrough upon rotation of said rotors thereby providing a flow of lubricating oil through said compressor that is proportional in magnitude to the speed of rotation of said rotors.

2. The combination as set forth in claim 1 wherein said metering chambers are formed in one end of the rotor with internal helical teeth, said discharge chamber being located at a radially outward location relative to the internal tooth rotor axis with a portion thereof covered by said internal tooth rotor and the other portion thereof communicating with the rotor cavity for the external tooth rotor.

3. The combination as set forth in claim 1 wherein said lubricating oil inlet chamber and said lubricating oil discharge chamber are located in a common wall and in a generally common plane, said common wall registering with and slidably engaging one end of each of said rotors.

4. The combination as set forth in claim 2 wherein said lubricating oil inlet chamber and said lubricating oil discharge chamber are located in a common wall and in a generally common plane, said common wall registering with and slidably engaging one end of each of said rotors. 

1. A rotary compressor for gaseous fluids comprising a first pump rotor with external helical teeth, a second pump rotor with internal helical teeth, the helical teeth on said rotors registering with each other as they rotate about parallel axes, a rotor housing, a pair of rotor chambers communicating with each other formed in said housing, one chamber receiving the external tooth rotor and the second chamber receiving the internal tooth rotor, said housing including an end wall closing said rotor chambers, said wall being disposed adjacent end suRfaces on said rotors, the end surface on one of said rotors having formed therein radially disposed metering chambers, a lubricating oil inlet chamber formed in said wall at a radial location where it is adapted to register with radially inward portions of said metering chamber, said lubricating oil inlet chamber being in fluid communication with a lubricating oil supply passage, a fluid discharge chamber formed in said wall at a radially outward location relative to the axis of rotation of said one rotor and arranged to register with the radially outward portions of said metering chambers as said rotors rotate, said discharge chamber being in communication with said rotor chambers whereby metered quantities of fluid are discharged therethrough upon rotation of said rotors thereby providing a flow of lubricating oil through said compressor that is proportional in magnitude to the speed of rotation of said rotors.
 2. The combination as set forth in claim 1 wherein said metering chambers are formed in one end of the rotor with internal helical teeth, said discharge chamber being located at a radially outward location relative to the internal tooth rotor axis with a portion thereof covered by said internal tooth rotor and the other portion thereof communicating with the rotor cavity for the external tooth rotor.
 3. The combination as set forth in claim 1 wherein said lubricating oil inlet chamber and said lubricating oil discharge chamber are located in a common wall and in a generally common plane, said common wall registering with and slidably engaging one end of each of said rotors.
 4. The combination as set forth in claim 2 wherein said lubricating oil inlet chamber and said lubricating oil discharge chamber are located in a common wall and in a generally common plane, said common wall registering with and slidably engaging one end of each of said rotors. 